A front-end module is typically a heterogeneous multi-chip module, a single package incorporating a plurality of chips, each of which uses one specific technology in fabrication and achieves a specific function in the front-end module. For example, a Wi-Fi or cellular handset front-end module frequently incorporates three or more chips to achieve low noise amplifier and/or switch, power amplifier, and digital control interface functions. Some front-end module may also incorporate a passive chip on an integrated passive device. Each of the chips employs a preferred technology that differs from each other to achieve competitiveness, both performance-wise and cost-wise. For example, heterojunction bipolar transistors (HBT) is a preferred technology for a power amplifier, pseudomorphic high electron mobility transistors (pHEMT) is a preferred technology for a low noise amplifier/switch, and CMOS is a preferred technology for digital control interface. High chip numbers and increased technology types inevitably elevate module level integration or packaging complexity and consequently raise the front-end module cost.
One common practice for lowering front-end module cost is to cut chip count. Using fewer chips to achieve the same functions with the same performance, however, typically requires combined or integrated technologies. For example, SiGe BiCOMS and GaAs BiFET are combinations of HBT technology and FET technologies. Totally front-end module cost reduction is not evident even an integrated technology allows a group of respective functions to be integrated into a single chip. The reason lies in that more process steps and larger mask counts of the integrated technology will significantly increase the chip fabrication cost. In fact, each of the functional blocks in the integrated chip actually uses almost exclusively a corresponding portion of the integrated technology. For example, a power amplifier functional block uses almost exclusively the HBT portion of the integrated BiCMOS technology while a bias/control interface circuit uses almost exclusively the CMOS portion of a SiGe BiCMOS process to implement a power amplifier and control interface. In some cases, the increased process steps increase the overall cost of the front-end module.